DATA VISUALISATION USING PYPLOT

[Pages:13]DATA VISUALISATION

USING PYPLOT

VISUALISATION : is the representation of an object, situation, or set of

information as a chart or other image (the formation of a mental image of something.)

Visualization is the easiest way to analyze and easily understand information. Python offers many graphics libraries that include lots of different features. Out of these library we are going to learn MATPLOTLIB.

MATPLOTLIB : Matplotlib is a Python 2D plotting library which produces

publication quality figures in a variety of hardcopy formats and interactive environments across platforms.

Why Matplotlib

Matplotlib can be used in Python scripts, the Python and IPython shells, the Jupyter notebook, web application servers, and four graphical user interface toolkits.

Matplotlib tries to make easy things easy and hard things possible. You can generate plots, histograms, power spectra, bar charts, errorcharts, scatterplots, etc., with just a few lines of code.

It supports Interactive and non-interactive plotting and can save images in several output formats (PNG, PS & Others) Pyplot module of matplotlib library supports a very wide variety of graphs and plots like histograms, barcharts power spectra, error charts etc. It is used

along with NumPy to provide an environment for MatLab. How to install Matplotlib

Python shell must be installed in your System

Open command prompt as an Administrator Go back to root directory by typing cd\ Now type pip install matplotlib

After successful installation, we are ready to use matplotlib and its modules

pg. 1 WWW.PYTHONCLASSROOMDIARY. BY SANGEETA M CHAUHAN, PGT CS KV3 GWALIOR

Lets Understand terms (Title,Labels, x label, y label etc) used for different sections in Plots/ Chart through this diagram .

/ LEGEND

Y- AXIS

X- AXIS

Using pyplot we can plot following type of charts :

S. PLOT/CHART NO NAME

EXAMPLE 1

Example 2

1 Line Chart

2.

Bar Chart (Vertical)

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3.

Bar Chart

(Horizontal)

4. Pie Chart

Some important Functions which are required to draw different Plots are :

S.No 1

Function Name plot()

Use

If you provide a single list or array to the plot() command, matplotlib assumes it is a sequence of y values, and automatically generates the x values for you. Since python ranges start with 0, the default x vector has the same length as y but starts with 0. Hence the x data are [0,1,2,3] .

2

xlabel()

3

ylabel()

4

title()

5

bar()

6.

barh()

7.

Pie()

8.

Figure()

Used to mention Xlabel with chart Used to mention Ylabel with chart To specify Title of the chart To draw bar chart To draw horizontal bar diagram To draw pie chart To specify size of plot area

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LINE GRAPH

1. A line Chart/Plot/Graph is a type of chart which displays information as a series of data points called 'markers' connected by straight line segments.

Lets take an example to draw Line Graph

The table shows passenger car fuel rates in miles per gallon for several years. Make a LINE GRAPH of the data. During which 2-year period did the fuel rate decrease?

YEAR: 2000 2002 2004 2006

RATE: 21.0 20.7 21.2 21.6

Solution

import matplotlib.pyplot as p Yr=[2000,2002,2004,2006] rate=[21.0,20.7,21.2,21.6] p.plot(Yr,rate) p.show()

Output :

You can change Line Style by specifying pattern with plot function. FOR EXAMPLE p.plot( Y, `--`) # To draw dashed line p.plot( Y,'-.') # To draw dash-dot line

In the above Figure it is not clear What is 2000,2002 etc, or 20.6,21.2...........So We should put Labels on it . To put Label we will do following changes in the Code

import matplotlib.pyplot as p

Yr=[2000,2002,2004,2006]

rate=[21.0,20.7,21.2,21.6]

p.plot(Yr,rate,color='red')

# To draw line in red colour

p.xlabel('Year')

# To Put Label At X Axis

p.ylabel('Rate')

# To put Label At Y Axis

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p.show()

With Label everything is clear

Now

BAR GRAPH:

A bar graph / bar chart/ bar diagram is a visual tool that uses bars(Vertical or Horizontal) to represent/compare categorical data. Let's take an example to make it clear

1. The number of bed-sheets manufactured by a factory during five consecutive weeks is given below.

Week Number of Bed-sheets

First Second Third Fourth Fifth

600

850

700

300 900

Draw the bar graph representing the above data. SOLUTION : PYTHON CODE

OUTPUT : fig 1

pg. 5 WWW.PYTHONCLASSROOMDIARY. BY SANGEETA M CHAUHAN, PGT CS KV3 GWALIOR

 We can draw grids also with the chart by adding p.grid(True)

with the above coding Output will be as follows Fig 1.1

If we want to plot Horizontal bar graph for the Same (above) question then we use

barh() Function and we have to interchange x and y labels as shown below

And Output will be as : fig 1.2

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2. The number of students in 7 different classes is given below. Represent this data on the bar graph.

Class Number of Students

6th

7th

8th

9th 10th 11th 12th

130 120 135 130 150 80 75

SOLUTION : PYTHON CODE

OUTPUT : fig 2

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3. The number of students and Pass percentage in 7 different classes is given below. Represent this data on the bar graph.

Class Number of Students

Pass Percentage

6th 130 70

7th 120 80

8th 135 76

9th 130 89

10th 150 90

11th 80 95

12th 75 100

SOLUTION : PYTHON CODE

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